Application of plasma polymerized siloxane films for the corrosion protection of titanium alloy

Organosilicon film and SiOx-like film are deposited on titanium alloy (Ti6Al4V) surfaces by atmospheric pressure (~ 105 Pa) dielectric barrier discharge to improve its corrosion resistance in Hanks solution. Hexamethyldisiloxane (HMDSO) is used to be the chemical precursor. The organosilicon film deposited in Ar/HMDSO system has high growth rate (75 nm/min) and low surface roughness (3 nm), while the SiOx-like film deposited in Ar/O2/HMDSO system has lower growth rate (35 nm/min) and slightly higher surface roughness (9 nm). The potentiodynamic polarization tests show that both the two siloxane films coated Ti6Al4V samples have more positive corrosion potential and one order of magnitude lower corrosion current density than the substrate, indicating the corrosion resistance of Ti6Al4V can be improved by depositing siloxane film on its surface. In particular, as the surface is more compact and cross-linked, the SiOx-like film has better corrosion resistance than the organosilicon film.